Over the last 5 years, plasmid profile analysis has become an accepted epidemiological tool used to characterize different strains of the same organism. The technique is particularly useful since it appears to be broadly applicable to many different groups of organisms. The first group of organisms we will be looking at are coagulase-negative staphylococci (CONS). All hospitals, including the Clinical Center, have noted a significant increase in the number of CONS associated with infection. Because this organism is also a frequent contaminant, it is often difficult to assess a particular isolate's significance, to identify relapse versus reinfection, or to identify infections in different patients caused by the same strain. Plasmid profile analysis may be useful in these instances. We have now developed several different methods which are capable of providing plasmid profiles for a variety of different groups of bacteria, including Staphylococcus aureus, S. epidermidis, Enteric Gram negative bacteria and Acinetobacter. The current methods are all comparatively simple and can be accomplished within 1 day. They all utilize a mini-gel procedure which is the basis for the very rapid turn-around time. Two plasmid projects have been initiated thus far. One is to determine the plasmid profile patterns of a group of Campylabacter jejuni isolates that were obtained from common variable hypogammaglobulinemia patients to add to the biochemical and serologic characterization of these strains which is also being done. The second investigation is into the usefulness of plasmid analysis in characterizing Staphylococcus haemolyticus significant isolates, many of which are very resistant to multiple antibiotics. Most of the plasmid work available in the literature of staphylococci involve S. aureus and S. epidermidis, so little is known about the usefulness of plasmid analysis for S. haemolyticus.